1. Field of the Invention
The present invention relates to an electrode catalyst for a fuel cell using a carbonaceous material of a special structure as an alternative catalyst for a precious metal catalyst such as platinum and relates to a fuel cell using the same.
2. Detailed Description of the Prior Art
As already known, in a solid polymer type fuel cell, a cell to be built in a cell module is comprised of a sheet-like solid polymer electrolyte film, an anode (fuel electrode) and a cathode (oxidant electrode) which are placed to oppose each other so as to hold this solid polymer electrolyte film in-between.
As the above-mentioned solid polymer electrolyte film, a fluorinated ion-exchange resin film representing a per-fluoro-sulfonic acid resin film (for example, Nafion film manufactured by DuPont) is used. Moreover, it is usual that the anode and the cathode (hereafter, simply called electrode(s)) are constructed comprising a catalyst layer and an electrode substrate containing a catalytic material, and are bonded on both principal surfaces of the solid polymer electrolyte film on the catalyst layer side by hot pressing.
For the electrode substrate mentioned above, a porous sheet (for example, carbon paper), which not only supports the catalyst layer, but also supplies and discharges reactant gases (fuel gas and oxidizer gas), and has also a function as a collector, is used. And, when the reactant gases are supplied to each of the above-mentioned electrodes, a three phase boundary of a gas phase (reactant gas), a liquid phase (solid polymer electrolyte film), and a solid phase (catalysts of both electrodes) is formed in the boundary between the catalyst layer carrying a platinum precious metal provided on both electrodes and the solid polymer electrolyte film, and thus an electrochemical reaction is caused to generate direct current power.
In the above-mentioned electrochemical reaction, the following reactions are caused, namely,                on the anode side: H2→2H++2e−        on the cathode side: (½)O2+2H++2e−→H2O,and H+ ion generated on the anode side moves toward the cathode side in the solid polymer electrolyte film, and e− (electron) moves to the cathode side via an external load. On the other hand, on the cathode side, the oxygen contained in the oxidizer gas reacts with H+ ion and e− having moved from the anode side, and thereby water is produced. Thus, a solid polymeric fuel cell generates direct current power from hydrogen and oxygen, and produces water.        